1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in association with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head of a structure in which a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
In order to improve the recording density in the performances of a recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring to FIGS. 37 to 42, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in FIG. 37, an insulating layer 102 made of, for example, aluminium oxide (Al2O3, hereinafter referred to as xe2x80x9caluminaxe2x80x9d) is deposited in thickness of about 5 to 10.0 xcexcm on a substrate 101 made of altic (Al2O3.TiC) or the like. Subsequently, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. For example, alumina is then deposited by sputtering in thickness of 100 to 200 nm on the bottom shield layer 103 to form a shield gap film 104. An MR film 105 for constructing an MR device for reproduction is deposited in thickness of tens nm on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers which are electrically connected to the MR film 105 are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104, and the MR film 105, so that the MR film 105 is buried in the shield gap films 104 and 106. An top shield-cum-bottom pole (hereinafter referred to as a bottom pole) 107 made of a magnetic material such as a nickel iron alloy (NiFe, hereinafter also simply referred to as Permalloy (trademark)) used for both of the reproducing head and the recording head is formed on the shield gap film 106.
As shown in FIG. 38, on the bottom pole 107, a write gap layer 108 made of an insulating material such as alumina is formed. Further, a photoresist film 109 is formed in a predetermined pattern on the write gap film 108 by high-precision photolithography. On the photoresist film 109, a thin film coil 110 for an inductive recording head made of copper (Cu) or the like is formed by, for example, plating. A photoresist film 111 is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist film 109 and the thin film coil 110. In order to insulate turns of the thin film coil 110 from each other, a heat treatment is performed at, for example, 250xc2x0 C. on the photoresist film 111.
As shown in FIG. 39, in a position rearward of the thin film coil 110 (right side in FIG. 39), to form a magnetic path, an opening 108a is formed by partially etching a part of the write gap layer 108 to expose a part of the bottom pole 107. A magnetic material having high saturated flux density, for example, Permalloy is selectively formed so as to cover the exposed face of the bottom pole 107, the photoresist film 111, and the write gap layer 108 by electrolyte plating. A photoresist film is formed on this plating film made of Permalloy and, after that, the photoresist film is subjected to a selective exposure process (photolithography process), thereby forming a photoresist film pattern (not shown) having a predetermined plane shape. By using the photoresist film pattern as a mask, the plating film is selectively etched by ion milling, thereby forming a top yoke-cum-top magnetic pole (hereinbelow, called top pole) 112. The top pole 112 has a plane shape as shown in FIG. 42 which will be described hereinlater, and includes a yoke portion 112a and a pole tip portion 112b. The top pole 112 is in contact with and magnetically coupled to the bottom pole 107 via the opening 108a. By using a part (pole tip portion 112b) of the top pole 112 as a mask, both the write gap layer 108 and the bottom pole 107 are selectively etched about 0.5 xcexcm by ion million (refer to FIG. 41). After that, an overcoat layer 113 made of, for example, alumina is formed on the top pole 112. Finally, a track surface, namely, an air bearing surface 120 of the recording head and the reproducing head is formed by a mechanical process and a polishing process. In such a manner, a thin film magnetic head is completed.
FIGS. 40 to 42 show the structure of the thin film magnetic head in a completed state. FIG. 40 is a cross section of the thin film magnetic head perpendicular to the air bearing surface 120. FIG. 41 is an enlarged cross section parallel to the air bearing surface 120 of the pole portion. FIG. 42 is a plan view of the structure. FIG. 39 is a cross section taken along line XXXIXxe2x80x94XXXIX of FIG. 42. In FIGS. 40 to 42, the overcoat layer 113 and the like are not shown. In FIG. 42, with respect to the thin film coil 110 and the photoresist film 111, only the outlines are shown.
FIGS. 40 and 42, xe2x80x9cTHxe2x80x9d denotes throat height. xe2x80x9cMRHxe2x80x9d denotes an MR height. The xe2x80x9cthroat height (TH)xe2x80x9d is one of factors determining the performances of the recording head and is a length from a position of the end on the side closest to the air bearing surface 120, of the insulating layer (photoresist film 111) for electrically isolating the thin film coil 110 from the other conductive portion, that is, the throat height zero position (TH0 position) to the position of the air bearing surface 120. In order to improve the performances of the recording head, it is necessary to optimize the throat height TH. The throat height (TH) is controlled according to a polishing amount at the time of processing the air bearing surface 120. An xe2x80x9cMR height (MRH)xe2x80x9d denotes a length from the position of the end on the side furthest from the air bearing surface 120, of the MR film 105, that is, the MR height zero position (MRH0 position) to the position of the air bearing surface 120. The MR height (MRH) is also controlled by the polishing amount at the time of processing the air bearing surface 120.
Factors determining the performances of the thin film magnetic head include not only the throat height (TH) and the MR height (MRH) but also an apex angle xcex8 shown in FIG. 40. The apex angle xcex8 is an average inclination angle of an inclined face on the side close to the air bearing surface 120 of the photoresist film 111.
As shown in FIG. 41, a structure in which a part of the write gap layer 108 and a part of the bottom pole 107 are etched in a self-aligned manner with respect to the pole tip portion 112b of the top pole 112 is called a trim structure. According to the trim structure, an increase in effective track width due to expansion of the magnetic flux generated at the time of writing data to a narrow track can be prevented. xe2x80x9cP2Wxe2x80x9d shown in FIG. 41 denotes a width of the portion having the trim structure (hereinbelow, simply called xe2x80x9cpole tip portion 500xe2x80x9d), that is, a pole width (hereinbelow, also called xe2x80x9ctrack widthxe2x80x9d). The process dimension of the pole width P2W depends on the width of the portion corresponding to the pole tip portion 500, of the mask (photoresist film pattern in the above case) used to perform an etching process for forming the trim structure. xe2x80x9cP2Lxe2x80x9d shown in the diagram indicates the thickness of the pole tip portion 112b as a part of the pole tip portion 500, that is, a pole length. As shown in FIG. 41, lead layers 121 as a lead electrode layer electrically connected to the MR film 105 are provided on both sides of the MR film 105. In FIGS. 37 to 40, the lead layers 121 are not shown.
As shown in FIG. 42, the top pole 112 has a yoke portion 112a which occupies a major part of the top pole 112 and a pole tip portion 112b having an almost constant width as the pole width P2W. In the coupling portion between the yoke portion 112a and the pole tip portion 112b, the outer periphery of the yoke portion 112a forms an angle xcex1 to a plane parallel to the air bearing surface 120. In the coupling portion, the outer periphery of the pole tip portion 112b forms an angle xcex2 to a plane parallel to the air bearing surface 120. For example, xcex1 is about 45 degrees and xcex2 is about 90 degrees. As described above, the pole tip portion 112b is a portion serving as a mask at the time of forming the trim structure of the pole tip portion 500. As understood from FIGS. 40 and 42, the pole tip portion 112b extends on the flat write gap layer 108, and the yoke portion 112a extends on a coil portion (hereinbelow, called an apex portion) which is covered with the photoresist film 111 and is raised like a hill.
The detailed structural characteristics of the top pole are described in, for example, Japanese Unexamined Patent Application No. 8-249614.
Since the pole width P2W of the pole tip portion 500 determines the recording track width on a recording medium, to increase the recording density, it is necessary to form the pole tip portion 500 with high accuracy and to narrow the pole width P2W. Especially, in recent years, in order to address a request of higher recording density, narrower pole width P2W which is, for example, about 0.3 xcexcm or less is desired. When the pole width P2W is too wide, a phenomenon such that data is written not only in a predetermined recording track area on the recording medium but also a neighboring area, that is, a side erase phenomenon occurs, so that the recording density cannot be improved. Consequently, it is important to make the pole width P2W of the pole tip portion 500 very narrow and constant over the whole area.
Methods of forming the top pole 112 include not only a wet process such as frame plating but also a dry process of selectively etching a plating film made of Permalloy by ion milling with a mask of a predetermined shape so as to be patterned.
In such a conventional dry process, however, the inventors of the present invention have recognized that the following problems occur.
1) For example, in the case of forming a mask used to pattern a plating film by a photolithography process, the minimum width of a portion corresponding to the pole tip portion 500 in a mask obtained is about 0.3 xcexcm for the following reason. When the width of the portion is set to be narrower than 0.3 xcexcm, the width becomes extremely too small with respect to the thickness (for example, 2 to 3 xcexcm), so that the mask cannot be formed according to the design dimensions. Consequently, in the case of using the above-described method, the limit of the minimum pole width P2W of the pole tip portion 500 formed finally is about 0.3 to 0.4 xcexcm. The very narrow pole width P2W (for example, 0.3 xcexcm or less) cannot be achieved.
2) In the case of etching the plating film by ion milling, for example, when an ion beam is emitted from a direction almost perpendicular to the surface of the plating film (direction at an angle of about 0 to 30 degrees in the width direction to the perpendicular line with respect to the surface of the plating film), an etch product generated at the time of etching adheres again to side walls which are not etched, and the width of the pole tip portion 112b is partially expanded more than the design value. On the other hand, when an ion beam is emitted from the direction almost parallel to the surface of the plating film (direction at an angle of about 50 to 70 degrees in the width direction to the perpendicular line with respect to the surface of the plating film), a phenomenon that the etch product adheres again as described above can be avoided. As the process progresses, however, the etch amount increases, and the width of the pole tip portion 112b becomes partially narrower than the design value. Particularly, when the pole tip portion 500 is formed by performing the etching process under the latter conditions, as shown in FIG. 43, the pole width P2W varies according to the positions in the thickness direction and becomes non-uniform.
3) When a photoresist film for forming a mask (photoresist film pattern) used for patterning the plating film is formed on a rough underlayer (Permalloy layer), reflection light in the oblique or lateral direction occurs from the surface of the underlayer. The reflection light expands or reduces the exposure area, thereby deteriorating the accuracy of forming the mask. One of the causes of deterioration in accuracy of forming the mask is that Permalloy having relatively high reflectance is uses as the material of the plating film as the underlayer of the photoresist film.
4) Since the pole tip portion 500 is formed by ion milling of which etching speed is slow, the etching process takes long time. A considerably long time is required to complete the process of the pole tip portion 500. Such a tendency is not limited to the case of forming the pole tip portion 500 but similarly occurs in the case of forming the top pole 112 and other magnetic layer portions (bottom shield layer 103, bottom pole 107, and the like).
There are, conventionally, not only the above-described problems in the process but also problems in performances. Specifically, Permalloy is conventionally used as a magnetic material of the magnetic layer portion constructing the thin film magnetic head. Consequently, when the pole width P2W is extremely narrowed to, for instance, about 0.3 xcexcm or narrower, a magnetic flux saturation phenomenon occurs particularly in the magnetic layer portion constructing the pole tip portion 500, so that a characteristic of overwriting data to a recording medium, that is, an overwrite characteristic deteriorates.
The invention has been achieved in consideration of the problems and its object is to provide a method of manufacturing a thin film magnetic head in which, particularly, the pole portion can be formed with high accuracy in a short time.
According to a first aspect of the invention, there is provided a method of manufacturing a thin film magnetic head including first and second magnetic layers magnetically coupled to each other and having first and second magnetic poles which face each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium, a thin film coil portion provided between the two magnetic layers, and an insulating layer for insulating the thin film coil portion from the two magnetic layers, wherein at least one of a step of forming the first magnetic pole and a step of forming the second magnetic pole includes: a step of forming a magnetic material layer; a step of forming a mask precursor pattern on the magnetic material layer; a first etching step of forming a first mask having a narrower width by etching a part of the mask precursor pattern by ion beam etching and, simultaneously, etching the magnetic material layer to a depth in an area other than an area where the first mask is formed; and a second etching step of forming at least one of the first and second magnetic poles by selectively etching the magnetic material layer by reactive ion etching with the first mask.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, in the first etching step, a part of the mask precursor layer is etched, thereby forming the first mask having a narrower width and, simultaneously, a layer near the surface of the magnetic material layer in an area other than the area of forming the first mask is partially etched. In the second step, the magnetic material layer is etched by reactive ion etching by using the first mask, thereby forming at least one of the first and second magnetic poles.
In the method of manufacturing a thin film magnetic head according to the first aspect of the invention, in the first etching step, an irradiation angle of an ion beam may be changed at least once. In such a case, during the first etching step, it is preferable to change an angle in the width direction between a direction orthogonal to an extending direction of the magnetic material layer and an irradiation direction of the ion beam from a first angle to a second angle which is larger than the first angle. Specifically, the first angle is set to an angle plus or minus 15 degrees of 45 degrees, and the second angle is set to an angle plus or minus 15 degrees of 75 degrees.
According to a second aspect of the invention, there is provided a method of manufacturing a thin film magnetic head including first and second magnetic layers magnetically coupled to each other and having first and second magnetic poles which face each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein at least one of a step of forming the first magnetic pole and a step of forming the second magnetic pole includes: a step of forming a magnetic material layer; a step of forming a mask precursor pattern on the magnetic layer; a first etching step of forming a first mask having a narrower width by etching a part of the mask precursor pattern by ion beam etching; and a second etching step of forming at least one of the first and second magnetic poles by etching the magnetic material layer by using the first mask by reactive ion etching.
In the method of manufacturing a thin film magnetic head according to the second aspect of the invention, in the first etching step, a part of the mask precursor layer is etched, thereby forming the first mask having a narrower width. In the second step, the magnetic material layer is etched by reactive ion etching by using the first mask, thereby forming at least one of the first and second magnetic poles.
In the method of manufacturing a thin film magnetic head according to the second aspect of the invention, preferably, in the first etching step, an ion beam is emitted from a direction at an angle plus or minus 15 degrees of 75 degrees in the width direction from a direction orthogonal to an extending direction of the magnetic material layer.
According to a third aspect of the invention, there is provided a method of manufacturing a thin film magnetic head including first and second magnetic layers magnetically coupled to each other and having first and second magnetic poles which face each other with a gap layer in between near and in a recording-medium-facing surface to be faced with a recording medium and each of which defines a recording track width of the recording medium, a thin film coil provided between the two magnetic layers, and an insulating layer for insulating the thin film coil from the two magnetic layers, wherein at least one of a step of forming the first magnetic pole and a step of forming the second magnetic pole includes: a step of forming a magnetic material layer; a step of forming a mask precursor pattern on the magnetic material layer; a first etching step of partially etching a layer near the surface of the magnetic material layer in an area other than an area of forming the mask precursor pattern by using the mask precursor pattern as a mask by ion beam etching; and a second etching step of forming at least one of the first and second magnetic poles by etching the magnetic material layer by using the mask precursor pattern as a first mask by reactive ion etching.
In the method of manufacturing a thin film magnetic head according to the third aspect of the invention, in the first etching step, a layer near the surface of the magnetic material layer in an area other than an area of forming the mask precursor pattern is partially etched. In the second step, the magnetic material layer is further etched by reactive ion etching by using the mask precursor pattern as the first mask, thereby forming at least one of the first and second magnetic poles.
In the method of manufacturing a thin film magnetic head according to the third aspect of the invention, in the first etching step, it is preferable to emit an ion beam from a direction at an angle plus or minus 15 degrees of 45 degrees in the width direction from a direction orthogonal to an extending direction of the magnetic material layer.
The method of manufacturing a thin film magnetic head of the invention may include a step of polishing the surface of the magnetic material layer so as to planarize the surface between the step of forming the magnetic material layer and the step of forming the mask precursor pattern.
In the method of manufacturing a thin film magnetic head according to the invention, a step of forming the mask precursor pattern may include: a step of forming a mask precursor layer on the magnetic material layer; and a third etching step of forming the mask precursor pattern by selectively etching the mask precursor layer by reactive ion etching. In this case, in the third etching step, a second mask having a shape corresponding to a plane shape of the mask precursor pattern may be used. In such a case, a photoresist film pattern having a predetermined plane shape may be formed on the mask precursor layer and used as the second mask., or a metal film pattern having a predetermined plane shape may be formed on the mask precursor layer and used as the second mask. Particularly, in the latter case, the metal film pattern may be formed by selectively growing a plating film on the mask precursor layer, or a metal layer may be formed on the mask precursor layer and selectively etched to thereby form the metal layer pattern. It is preferable to use any of nickel iron, nickel copper, iron nitride, cobalt iron, nickel boron and nickel phosphor as a material of the metal film pattern.
In the method of manufacturing a thin film magnetic head according to the invention, in the first etching step, the second mask may be also etched and removed.
In the method of manufacturing a thin film magnetic head according to the invention, the mask precursor layer may be deposited by chemical vapor deposition. In such a case, it is preferable to deposit the mask precursor layer under a pressure of 100 Pa or lower.
In the method of manufacturing a thin film magnetic head according to the invention, a predetermined inorganic material may be used as a material of the first mask. In such a case, as the inorganic material, it is preferable to use a material containing aluminum oxide or aluminum nitride.
In the method of manufacturing a thin film magnetic head according to the invention, in the case where the first magnetic pole extends in a direction apart from the recording medium facing surface and defines a recording track width of the recording medium, and the first magnetic layer includes a first magnetic layer portion having the first magnetic pole and a second magnetic layer portion which covers an area of the thin film coil and is magnetically coupled to the first magnetic layer portion, a plane shape of the first mask may include at least a portion corresponding to the plane shape of the first magnetic pole in the first magnetic layer portion.
In the method of manufacturing a thin film magnetic head according to the invention, in the case where the first magnetic layer portion further includes an expanded portion which is magnetically coupled to the first magnetic pole on the side far from the recording medium facing surface and is wider than the first magnetic pole, a step in the width direction is formed in a position where the first magnetic pole and the expanded portion are coupled to each other, and a corner is formed at a part where a side face of the first magnetic pole and a step face of the expanded portion in the step cross each other, preferably, the plane shape of the first mask further includes a part corresponding to a plane shape of the expanded portion, and an angle at a part corresponding to the corner of the first magnetic layer portion in the first mask lies in a range from 90 degrees to 120 degrees.
In the method of manufacturing a thin film magnetic head according to the invention, in the third etching step, it is preferable to perform an etching process in a gas atmosphere containing at least one of carbon tetrafluoride, sulfur hexafluoride, boron tribromide, chlorine, and boron trichloride at a temperature in a range from 50 degrees to 300 degrees.
In the method of manufacturing a thin film magnetic head according to the invention, in the second etching step, at least the first magnetic pole in the first magnetic layer may be formed, or the second magnetic pole in the second magnetic layer may be formed.
In the method of manufacturing a thin film magnetic head according to the invention, an area other than an area for forming the first magnetic pole in the gap layer may be selectively removed by reactive ion etching. In such a case, it is preferable to continuously perform formation of the first magnetic pole in the first magnetic layer, selective removal of the gap layer, and formation of the second magnetic pole in the second magnetic layer in the same step. In the case of processing the portions, preferably, the first magnetic pole in the first magnetic layer is formed by using a first mask made of a predetermined inorganic material, and the selective removal of the gap layer and formation of the second magnetic pole in the second magnetic layer are performed by using at least one of the first mask and the first magnetic pole as a mask.
In the method of manufacturing a thin film magnetic head according to the invention, in the step of forming the first magnetic layer, the second magnetic layer portion may be formed separately from the first magnetic layer portion by reactive ion etching. In such a case, it is preferable that the second magnetic layer portion is partially overlapped with a part of the first magnetic layer portion, and an end on the side near and in the recording medium facing surface, of the second magnetic layer portion is positioned apart from the position of the recording medium facing surface.
In the method of manufacturing a thin film magnetic head according to the invention, in the case where the thin film coil has a first thin film coil layer and the insulating layer has a first insulating layer portion which buries the first thin film coil layer, the method may include: a step of forming the first insulating layer portion so as to cover at least the first magnetic layer portion and the first thin film coil layer; and a step of forming a first planarized face by polishing a surface of the first insulating layer portion until at least the first magnetic layer portion is exposed. In such a case, the second magnetic layer portion may be formed on the first planarized face.
In the method of manufacturing a thin film magnetic head according to the invention, when the first magnetic layer further includes a third magnetic layer portion for magnetically coupling the first magnetic layer portion and the second magnetic layer portion between the first and second magnetic layer portions, the third magnetic layer portion may be formed on the first planarized face by reactive ion etching. In such a case, preferably, the third magnetic layer portion is overlapped with both a part of the first magnetic layer portion and a part of the second magnetic layer portion and an end on the side close to the recording medium facing surface, of the third magnetic layer portion is positioned apart from the position of the recording medium facing surface.
In the method of manufacturing a thin film magnetic head according to the invention, when the thin film coil portion further has a second thin film coil layer disposed in a layer different from the first thin film coil layer, and the insulating layer further has a second insulating layer portion for burying the second thin film coil layer, the method may include: a step of forming the second thin film coil layer and forming a first connection pattern serving as a part of the thin film coil portion integrally with the second thin film coil layer at an end of the second thin film coil layer; a step of forming a second connection pattern serving as a part of the thin film coil portion on the first connection pattern in the same step of forming the third magnetic layer portion; a step of forming the second insulating layer portion so as to cover at least the third magnetic layer portion, the second thin film coil layer, and the second connection pattern; a step of forming a second planarized face by polishing a surface of the second insulating layer portion until both at least the third insulating layer portion and the second connection pattern are exposed; and a step of forming a conductive layer pattern so as to be electrically connected to an exposed face of the second connection pattern on a part of the second planarized face. In such a case, the second magnetic layer portion may be formed in another part on the second planarized face.
In the method of manufacturing a thin film magnetic head according to the invention, when the head further has: a magnetic transducing function device film extending in a direction apart from the recording medium facing surface; and a third magnetic layer for magnetically shielding the magnetic transducing function device film, the third magnetic layer may be formed by an etching process of reactive ion etching.
In the method of manufacturing a thin film magnetic head according to the invention, the magnetic material layer may be deposited by sputtering by using a predetermined magnetic material. In such a case, as the magnetic material, it is preferable to use a material containing iron nitride or an amorphous alloy such as a material containing iron cobalt zirconium oxide alloy.
In the method of manufacturing a thin film magnetic head according to the invention, in the second etching step, it is preferable to perform an etching process in a gas atmosphere containing at least one of chlorine, boron trichloride, and hydrogen chloride at a temperature in a range from 50 degrees to 300 degrees.
Other and further objects, features and advantages of the invention will appear more fully from the following description.